The complete blood cell count (CBC) is the most commonly ordered diagnostic test in the ambulatory and emergency room settings. While there are multiple commercially-available point-of-care (POC) systems that measure individual components of a CBC, current systems do not provide the complete CBC but even more importantly, these POC systems do not integrate multiple additional assays using the same blood sample. For these reasons, the CBC continues to be performed almost exclusively in central laboratories using multiple milliliter-scaled blood samples. This offers a tremendous opportunity to provide the complete CBC along with other critical analytes for routine blood monitoring in the POC environment. Furthermore, ideal sample volumes required to measure these critical laboratory values in children should come from a heel or finger stick, consistent with those amounts necessary for microfluidic technologies. This will be a tremendous benefit to pediatric patients by reducing the blood volumes and resulting requirements for blood transfusion, as well as a reduction in turn-around-time and human error in sample processing. The goal of this proposal is to demonstrate the feasibility of a compact, operationally simple flow cytometer module capable of performing a full CBC and five-part white blood cell (WBC) differential. GF has developed a microfluidic flow cytometer which incorporates a reusable flow-cell chip with integrated optics and fluidics that is capable of measuring all but one component of a full CBC. In the proposed project, GF together with Lawrence Livermore National Lab (LLNL) will develop and manufacture a second generation microfluidic chip eliminating the surface roughness and variability, which plagued the manufacturing of the first generation chip. The specific aims for this proposal are: Specific Aim 1: Design a second generation integrated optical and fluidic chip. The chip will be redesigned to reduce background scattering, optimize the capture of scattered light and to be compatible with cutting edge scalable manufacturing techniques. Specific Aim 2: Manufacture the second generation chip in collaboration with LLNL. The microfluidic chip will be manufactured by our partners at LLNL, ensuring quality control and feasibility for large scale manufacturing. Specific Aim 3: Validate the flow cytometer with discard adult patient samples from MGH. A clinical comparison, with more than 250 discard adult patient blood samples from MGH, tested with GF's microfluidic cytometer and the MGH central laboratory.